1. Field of the Invention:
The invention relates to medicaments for therapy of skin disorders. These medicaments may include materials which are known for the treatment of skin disorders, and are used as external topical agents on the skin. The invention also relates to medicaments for non-skin disorders, in which the medicaments are applied transdermally.
2. Discussion of the Background:
As a rule, ointments, creams, lotions or tinctures which incorporate specific active ingredients, are used topically for skin disorders. A prerequisite for the therapeutic effectiveness of these active ingredients is that they are liberated in therapeutic amounts from the respective matrix. Only if this occurs can the active ingredients penetrate into the skin and from there reach the sites at which their activity is required.
Liposomes are novel medicinal vehicles. Liposomes are defined as spheroidal structures comprised of one or more lipid double layers, and having an aqueous interior cavity. They may be prepared from phospholipids, for example, lecithin by mechanical breakdown to produce fine particles. Techniques for preparing liposomes, and use of liposomes as pharmaceutical or cosmetic vehicles with the active ingredients deposited in the interior cavities of the liposomes, are described in U.S. Pat. No. 3,957,971, German No. OS 28 18 655, German No. OS 28 34 308 and British Pat. No. 2,013,609. The state of the art in 1982 regarding the preparation of liposomes and their use as pharmaceutical vehicles is disclosed in Pharmazie in unserer Zeit 11:97-108 (1982). According to the latter article, application of pharmaceutical-containing liposomes has been tested by intravenous, intramuscular, and subcutaneous injections, and also by oral administration.
There is, therefore, a prejudice in the art against the testing of medicinal formulations using liposomes as the vehicle wherein such formulations are applied locally on the skin, e.g., topical application in skin disorders. This is based on the knowledge of skin structure and extensive experience with skin application. Specifically, the prejudice against topical application relates to the presence, underneath the stratum corneum (the horny superficial layer of the skin), of a denser layer of cells, the stratum conjunctum or stratum compactum, having the function of impeding penetration or substances from the exterior.
The most frequently used active ingredients in external treatment of skin disorders are corticosteriods and trihydroxyanthracenes. However, these materials have low penetrability through the skin after being liberated from their vehicles. Therefore, when they are employed in, for example, ointments or creams they must be present in relatively high concentration and large excess in order to achieve an adequate therapeutic effect.